As a structure which performs braking of a caster, a structure which presses a brake shoe against a tread surface of the caster to stop rotation of a wheel has been known (Japanese Unexamined Patent Application Publication No. Sho 56-63501).
On the other hand, there is also known a structure having lock receiving parts which concentrically have small diameters, are formed like internally toothed gears, and annularly aligned on a side surface of a wheel, a protruding part being ejected from or retracted into the lock receiving parts to brake the wheel (Japanese Unexamined Patent Application Publication No. 2001-1703).
However, when any one of these braking structures is used, there is fear that braking is not effective when a heavy load is applied to a caster.
Thus, in a double-lock caster disclosed in Japanese Unexamined Patent Applicant Publication No. 2008-1355, the present applicant has proposed, as a structure having a braking mechanism doubly provided to a caster, a structure having a first brake shoe which is pivoted to a support yoke pivotally supporting a wheel, can displace a lock member pivoted to the support yoke between a first braking position at which the lock member abuts against a tread surface of the wheel and a first-braking release position at which the lock member is away from the tread surface, and is energized in a direction of the first braking release position to serve as a first brake, and a brake plate which is interlockably coupled with the lock member, slidable so that it can move forward and backward along the support yoke, advances to a second braking position at which an engagement part at a distal end is engaged with an engagement receiving part formed of continuous irregularities annularly formed on an inner peripheral side surface of the wheel when the brake shoe is displaced to the first braking position, retreats to a second braking release position at which the engagement part is separated from the engagement, receiving part when the brake shoe is displaced to the first braking release position, and is energized in a direction of the second braking release position.
Further, the brake plate is disposed to the inner side of a side surface of the support yoke and has a long hole into which an axle of the wheel is fitted and which is set to a length of a sliding stroke of the brake plate, a guide part which guides sliding of the brake plate is provided on an inner wall surface of the support yoke or the brake plate, and the brake plate is advanced or retreated in an up-and-down direction along a diametric direction of the wheel to engage the engagement part with the engagement receiving part.
In the above-described structure, a folded part of a swiveling lock piece constituted of a spring material formed into a pin shape having upper and lower pieces is disposed to the support yoke, the swiveling lock piece is configured to be latched to the lock member in a state where the upper and lower pieces are opened, the brake plate has a complicated structure since an upper part of the brake plate is interlockably coupled with the lock member, and regulation of swiveling alone cannot be performed separately from braking.